Posted by Anonymous on .
Evaluate the indefinite integral.
∫ sec^3x tanx dx
I let u=tanx
took derivative..
du=sec^2x dx
..now what??

Calculus 
helper,
sec^3 x tan x dx
 = integral symbol
Rewrite as
 sec^2 x sec x tan x dx
u = sec x
du = sec x tan x
 u^2 du
1/3 u^3 + C
Substitute back in, u = sec x
1/3 sec^3 x + C